The present invention relates to a drill comprising a drill body provided with a drill tip having cutting elements and chip flutes, said drill tip being detachably attached to the front surface of the drill body by fasteners whereby a rear surface of the drill tip and the front surface of the drill body have a centrally located tap or extension and a corresponding recess. The invention also relates to the drill tip per se which is intended to be secured to a drill body.
A drill of the aforementioned type is disclosed in Roos U.S. Pat. No. 4,684,298 wherein a replaceable drill tip is provided with an integral tap or extension which, however, requires a very high manufacturing accuracy in order to assure that the extension and the recesses for the fastening means provided on the tip shall be linearly oriented with corresponding recesses in the drill body. The hard metal of the drill tip is very sensitive to being forced, and the integral tap of the prior drill tip has, therefore, often become broken during the drilling operation. This prior drill also is equipped with fastening means having central flushing channels. These fastening means must therefore be provided with relatively large cross-section diameters to include the channels. This results in a correspondingly reduced thickness of material at the drill tip which reduces its strength.
It is, therefore, a purpose of the present invention to provide a drill with easily exchangeable cutting elements. It is another purpose of the invention to provide a drill with an accurately oriented drill tip.
It is another purpose of the invention to provide a drill with a reliable connection between the drill body and its associated drill tip.
It is another purpose of the invention to provide a drill tip with improved strength.
It is yet another purpose of the invention to provide a drill tip having externally provided flushing channels in order to transmit flushing medium.